A new approach to the construction of second-order nonlinear optical (NLO) materials has been described in U.S. Pat. No. 5,156,918. This method involves the covalent self-assembly of intrinsically acentric multilayers of high-.beta. chromophores on inorganic oxide substrates. Such robust thin film superlattices exhibit high second harmonic generation (SHG) efficiencies with .chi..sub.zzz values for 25 .ANG. thick monolayers of 5-7.times.10.sup.-7 esu at h.omega.=1.17 e V. This level of response is higher than that of conventional inorganic oxides such as LiNbO.sub.3 and rivals or exceeds that of the most efficient poled polymers and acentric Langmuir-Blodgett films. Importantly, the self-assembled thin films are thermodynamically equilibrated systems and thus do not require an external aligning electric field to establish an acentric environment. This property represents a major processing advance over poled NLO polymers where inducing and completely stabilizing net chromophore alignment has been shown to be difficult. In addition, the present self-assembled chromophoric thin films are thermally and mechanically very robust--more so than typical chromophoric Langmuir-Blodgett films.